The present invention relates generally to fasteners and more particularly to a fastener with a plastic polymer layer covering at least a portion of a bearing surface.
Fasteners are used in numerous applications to attach various components together. Typically, a fastener has at least a threaded portion and one or more bearing surfaces attached thereto. The bearing surfaces are designed to receive torque from a tool, such as a socket or other wrench, which is used to tighten or loosen the fastener. In a conventional fastener, such as a nut, the fastener may have internal threads and six bearing surfaces oriented in a hexagonal shape around the internal threads. However, other fasteners may have external threads, such as bolts and screws. Fasteners may also have a different number of bearing surfaces as desired.
Aesthetics is one concern for certain fasteners, such as automobile wheel nuts. In particular, many automotive consumers are drawn to the aesthetics of an automobile's wheels, since this is often a distinctive part of an automobile. As a result, the wheel nuts become an integral component of the aesthetics of the wheel, and the automobile more generally, because the wheel nuts form a highly visible pattern around the center of the wheel.
One approach that has been highly successful in addressing wheel nut aesthetics is stainless steel capped wheel nuts. In this solution, a nut insert is capped with a stainless steel covering. Since stainless steel is resistant to corrosion, highly durable and visually attractive, stainless steel capped wheel nuts have been capable of addressing a large portion of the demand for aesthetically pleasing wheel nuts. Another advantage of stainless steel capped wheel nuts is that the color of stainless steel, a shiny silverish color, generally matches the color used for most automobile wheels.
A broader design trend in consumer aesthetics is to offer a variety of different color schemes that a consumer can choose from according to the consumer's individual aesthetic interests. However, manufacturing fasteners with different color schemes has been difficult. In particular, the surfaces of a fastener's bearing surfaces must be highly durable to withstand the wrenching forces that are applied to the fastener during tightening and loosening. This is particularly a concern with the automotive wheel nuts because automotive wheel nuts are a critical safety feature of an automobile and automobile wheel nuts are commonly subjected to especially high tightening and loosening torques.
Conventional colored coatings have generally been unsatisfactory for automotive wheel nuts. For example, some metal adhering coatings, such as paint, plating, chemical treatments and the like, are available, but most of these lack sufficient durability or are unattractive aesthetically. In particular, while paint and other coatings are often available in a wide variety of colors, many of these coatings crack when high wrenching forces are applied to the coating. As a result, the body of the fastener becomes exposed to the environment through the cracked coating. This will eventually lead to visible corrosion of the body and diminish the aesthetics of the automobile. On the other hand, coatings that have been found to being more durable are not available in attractive color choices, and are mostly useful for preventing corrosion on less conspicuous parts.
Another alternative that has been used is caps that are snapped or screwed onto a fastener after the fastener has been tightened. This design has become disfavored, however, and is not widely used because the plastic caps tend to fall off the fastener over time and become lost. This design is also less convenient because the cap is a separate piece that must be assembled onto the fastener after the fastener is tightened and must be removed from the fastener in order to loosen the fastener.
Accordingly, the inventors believe that it would be desirable to provide an improved fastener that is aesthetically attractive to consumers.